Anyone watch Mike Larabee coaching 3rd base? He's not too shy about helping his batters gain an advantage.
Take a hint as a coach - if another team is stealing your signs, devise a better system. At younger ages though, a parent sitting behind the backstop yelling things to "help" his daughter's team is nothing but a big embarassment - to himself, his DD and her team. Rarely does this help a 10 or 12 year old girl batting. If this parent were on a team of my DD's, I would seriously ask our coach to politely tell him to "put a damper on it".
This parental involvement usually goes away around 14u and up, especially on the top competitive teams. The parents either figure out that they are hurting their DD and her team with their antics, or they get banned from the better teams. A rule should be added to ALL softball rule books: Coaches coach; Parents spectate.